Catalan.scala

object Catalan {
    def myCatalan(m:Int, n:Int, accum:Int):Int = {
        (m>0 && n>0, m==n) match {
            case (false, _) => accum
            case (_, true) => myCatalan(m, n-1, accum + 1)
            case (_, false) => myCatalan(m-1, n, accum + 1)
        }
    }
}